Digital Enhanced Cordless Telecommunications is a standard developed by the European Telecommunication Standard Institute from 1988, governing pan-European digital mobile telephony. DECT covers wireless PBXs, telepoint, residential cordless telephones, wireless access to the public switched telephone network, Closed User Groups (CUGs), Local Area Networks, and wireless local loop.
The DECT Common Interface radio standard is a multicarrier time division multiple access and time division duplex (MC-TDMA-TDD) radio transmission technique. The technique uses ten radio frequency channels from 1880 to 1930 MHz, each divided into 24 time slots of 10 ms, and twelve full duplex accesses per carrier.
A DECT base station (an RFP, Radio Fixed Part) can transmit all 120 possible accesses by using different frequencies or using only one frequency. All signaling information is transmitted from the RFP within a multi-frame (16 frames). Voice signals are digitally encoded into a 32 kbit/s signal using Adaptive Differential Pulse Code Modulation.
FIG. 1 shows a time slot data format in the DECT Radio Communication system. “P” represents a preamble field. “S” represents a synchronized field. “A” represents a protocol related signal field called Frame A for short. “B” represents the user data/voice field called Frame B for short. And in the specification below, C/L represents connectionless.
The DECT Radio Communication system presently provides two kinds of C/L downlink services. The C/L refers to the connective state that the portable terminal doesn't respond to the base station while the portable terminal is locked with the base station. Corresponsively, the connection-oriented refers to the connective state that the portable terminal responds to the base station while the portable terminal is connected with the base station. The first kind of C/L downlink service (SHORT) doesn't influence the proceeding data/voice transmission by using frame A to transmit information, but it is only suitable for the short information transmission. The second kind of C/L downlink service (LONG) is suitable for the long information transmission by using frame B to transmit information, but it influences the proceeding data/voice transmission. The influenced voice is harsh to humans' ear.
Generally, the first technology mentioned above is used to broadcast information to all terminals. The second technology is used to broadcast information to specific terminals for avoiding the interference problem.
As shown in FIG. 2, the MAC (media access control) layer has five logical channels, P, Q, N, M and C. P channel is the MAC paging channel. Q channel is the system information channel. M channel is the MAC layer control channel. N channel is the identities channel. C channel is the Higher layer (data link control) information channel. These logical channels transmit following the T-MUX algorithm as shown in FIG. 2. FIG. 2 shows that P channel transmits messages only during the 0th, 2nd, 4th, 6th, 10th, 12th frames. To distinguish the difference between message and information in the specification below, the paging data on P channel is called message and the data sent by the C/L service is called information.
Furthermore, the first message on the P channel must be transmitted during the 0th frame within a multi-frame. If there exists a need to transmit paging message within the following frames, the system will need to set values in extend flags within the format except the 12th frame. The extend flag within the 12th frame is set to 0. Those are the particular using rule of P channel.
FIG. 3 discloses the DECT MAC layer P channel paging format. FIG. 3(a) discloses the page format of the full-length page message. FIG. 3(b) discloses the paging format of the short paging message. FIG. 3(c) discloses the paging format of the zero length paging message. When the full-length message is transmitted, the paging format of the full-length message includes extend flag frame (1 bit), length information frame (3 bits) and paging data frame (36 bits). When the short paging message is transmitted, the paging format of short page message includes extend flag frame (1 bit), length information frame (3 bits), paging data frame (20 bits), info-type (4 bits) and MAC layer information (12 bits). When the zero length paging message is transmitted, the paging format of zero length page message includes extend flag frame (1 bit), length information frame (3 bits), base station identification number least significant 20 bits frame (20 bits), info-type (4 bits) and MAC layer information (12 bits).